How the Bali bombers were caught

AT first horrifying glance, piecing together the evil deeds of the Bali bombers appeared an almost impossible "Mt Everest" for the Australian Federal Police to attempt.

A decade on, it can be revealed just how the terror plot behind Australia's biggest murder investigation began to unravel - starting with tiny, shredded fragments of tartan.

As former AFP forensic chemist David Royds explains, it was in the smallest details and "what wasn't there and should have been" which exposed the identities of the suicide bombers and those who behind the October 12, 2002 attacks on Paddy's Bar and the Sari Club which claimed the lives of 202 people, 88 of them Australians.

The first bombsite at Paddy's Bar yielded some of its shocking clues to Royds and a small "alliance" of Australian and Indonesian investigators almost immediately.

Besides the physical carnage, the shocking scene was a chaotic ruin of scattered personal belongings, burned bar stools and other fire damage, what he didn't find was more significant.

No splintered furniture or concrete floor craters, indicating the bomb must have been off the ground when it was detonated to unleash its fury on the unsuspecting staff and holidaymakers.

Blood splatterings on the bar's cement ceiling would confirm the DNA belonged to just one person: a lone suicide bomber sent on his heinous martyr mission by the Al Qaeda-aligned terror group, Jemaah Islamiyah.

Royds says he was initially advised against going public with his suicide bomber theory by ASIO colleagues, with the Indonesian Government back then in denial of JI's hateful activities in south-east Asia.

But it was the shredded tartan, found embedded in trace evidence around the bomb's epicentre, which would offer surprising proof, later revealed as the cotton lining of the bomber's vest.

Finding these minute details - and others revealed in Channel 9's AFP Bali special tonight - was a testament to the meticulous, committed work of those charged with finding the terrorists responsible.

Royds and AFP assistant commissioner Tim Morris, who lead the AFP operation in Bali, both admit they thought solving the crime may never happen.

"At the time I was fairly pessimistic, I didn't think we had a chance," Royds, now a lecturer at Canberra University, said yesterday.

"Some of these guys had six or seven aliases and I couldn't pronounce one of them. It was so hard, I found it really, really stressful."

As the master bombmaker, Dr Alzahari and accomplice Noor Din Mohd Top continued their reign of terror over the next three years, Morris says he was haunted by the thought: "what if we never catch them?"

He paid tribute to the joint efforts of more than 650 AFP staff, state coroners and forensic police from across Australia and "professionals drawn in from all walks of life who contributed to some pretty incredible outcomes."

But for all the investigation's success, Royds added: "I just wish it never happened."